The invention relates to injection devices and methods, including, an injection device that comprises a lockable dosing member for the dosed administration of an injectable product. In some embodiments, the injection device particularly serves the self-administration of the product. Preferably, it serves the administration of a parathyroid hormone, for example heparin, in the treatment of osteoporosis. However, a device in accordance with the present invention can also be used in other therapies, for example for the administration of insulin in diabetes therapy. In some preferred embodiments, the injection device has overall the shape of a pen.
Not least due to their comfortably manipulable shape, injection pens are widely used especially in the self-administration of medicaments. In self-administration, simple manipulability, precision and certainty in dosing, along with the lowest possible price of the device, become of great importance.
WO 02/30495 A2 discloses an injection pen developed specifically for osteoporosis therapy. The medicament is conveyed from an ampoule by means of a piston. The driving of the piston is effected by mean of a piston rod, which is held in a housing of the pen so as to be axially displaceable in a straight manner. The medicament, as is normally the case with injection pens, is discharged by a propulsion stroke carried out in common by the piston rod and the piston. The length of the stroke determines the dose administered each time the medicament is discharged. The setting of the dose is the function of a dosing member, which together with the piston rod forms a spindle drive. Through a rotary movement of the dosing member, the length of the propulsion stroke is adjusted.
For the setting of the dose, in a first step, the dosing member must be rotated into a first catch engagement, in which it is locked with the housing in a zero dose position and from which the dose can be adjusted in a next step.
In order to exhaust the air from the product-guiding parts of the pen before an administration, for example after an ampoule change or a refilling of the ampoule, i.e., in order to perform a priming, the dosing member can be rotated out of the zero dose position and, instead of being moved to a fixed end stop that defines a maximum dose, rather may be moved into a priming position by means of a relatively short dosing rotary movement. In the priming position, it is in a second catch engagement with the housing.
The dosing rotary movement of the dosing member effects, via an appropriate coupling to the housing and by virtue of the straight guiding of the piston rod, a superimposed backward movement of the dosing member relative to the housing and relative to the piston rod.
The catch mechanism is formed by axially-extending V-grooves formed in regular distribution over an outer peripheral surface of the dosing member, which grooves are engaged from the outside by a finger formed by the housing. The finger is elastically bendable in a radially-outward manner and, during the dosing rotary movement, snaps from one V-groove into another. For the adjustment of the dose, the finger must first click into the longest of the V-grooves, so that the dosing member assumes a zero dose position, from which it can then carry out a first, purely translational backward movement with the finger engaging the V-groove, which movement brings the dosing member into engagement with a thread formed on the housing. Only the engagement with this thread causes the axial backward movement required for the adjustment of the discharge stroke to be superimposed by the dosing rotary movement of the dosing member. The dosing mechanism meets the requirements placed on it from a functional point of view, but is very complex.
Another injection pen with lockable dosing member is known from WO 96/07443 A1. In this pen, the dose is adjusted by means of a dosing rotary movement of the dosing member, on which movement an axial translational movement is superimposed. With the aid of a catch mechanism between the dosing member and a latch attached in a hinged manner to the housing of the pen, different doses can be set. The catch mechanism serves in the first instance to secure the dosing member in the zero dose position. The dosing member is provided on an outer peripheral surface with grooves arranged axially in a row. The latch can form a catch engagement with each of these grooves by snapping forth into the respective groove. In order to be able to withdraw the dosing member out of the housing of the pen from the zero dose position into a proximal end position, the latch must be operated. From the proximal end position, the desired dose can be set in that, through the dosing rotary movement, the dosing member is turned back again in the distal direction, i.e., into the housing, by a desired path length along a spindle. During this dosing rotary movement, the catching of the latch in the grooves of the dosing member produces an audible clicking and, in addition, offers a certain security against an inadvertent rotation of the dosing member. However, this known dosing mechanism is quite complex, and the latch attached to the outside of the housing may cause problems.